1. Field of the Invention
This invention relates to an image forming apparatus.
2. Description of Related Art
In conventional image forming apparatuses of so-called tandem type, toner images formed on a photosensitive drum in each image forming unit, or each image drum unit, are transferred onto a medium such as printing paper conveyed by a transfer belt or onto a transfer belt.
Speed irregularity, however, may occur due to contraction and expansion of a belt material structuring the transfer belt or due to deviations of frictional coefficient of drive rollers for driving the transfer belt, thereby resulting deviations with respect to the designed value of the speed of the transfer belt. Such speed deviations of the transfer belt may affect the conveyance speed of media, so that images printed on the medium may be suffered from contraction and expansion of images in a sub-scanning direction (see, e.g., Japanese Patent Application Publication (A1), No. 2014-025962).